diff --git a/gatewayBackend.php b/gatewayBackend.php
index 8fa4b86..a74b319 100644
--- a/gatewayBackend.php
+++ b/gatewayBackend.php
@@ -9,11 +9,52 @@ interface gatewayBackend
 	 * @param String $sessionId
 	 * @return String $token
 	 */
-	public function get_token($username, $password, $ip, $sessionId);
+	public function getToken($username, $password, $ip, $sessionId);
+        
+        /**
+         * 
+         * @param String $token
+         * @param String $sessionId
+         * @param String $ip
+         * @return Boolean
+         */
+        public function checkToken($token, $sessionId, $ip);
+        
+        /**
+         * removeToken() Remove a logged out user's token
+         * 
+         * @param String $token
+         */
+        public function removeToken($token);
 
 	/**
-	 * @param
+         * sendSMS()
+         * 
+         * Send SMS message to recipient's phone number
+	 * @param String $token
+         * @param String $recipient
+         * @param String $message
+         * @param Array $passwordLocations
+         * @return Boolean
 	 */
-	public function 
+	public function sendSMS($token, $recipient, $message, $passwordLocations);
+        
+        /**
+         * auditLog() Log audit messages
+         * 
+         * @param String $ip
+         * @param String $event
+         * @param String $message
+         */
+        public function auditLog($ip, $event, $message);
+        
+        /**
+         * messageLog() Log sent messages
+         * 
+         * @param String $recipient
+         * @param String $message
+         * @param String $ip
+         */
+        public function messageLog($recipient, $message, $ip);
 }
 
diff --git a/postgresGatewayBackend.php b/postgresGatewayBackend.php
index 04749e8..3e4ae05 100644
--- a/postgresGatewayBackend.php
+++ b/postgresGatewayBackend.php
@@ -1,7 +1,61 @@
 <?php
 require_once 'gatewayBackend.php';
 
-class postgresGatewayBackend implements gatewayBackend
+final class postgresGatewayBackend implements gatewayBackend
 {
+    const GWBE_SUCCESS  = 0;
+    const GWBE_DBERROR  = 1;
+    const GWBE_AUTHFAIL = 2;
+
+    private $dbh = null;
+
+    public function __construct($dbHost, $dbUser, $dbPassword, $dbName)
+    {
+        $dsn = 'pgsql:host=' . $dbHost . ';dbname=' . $dbName;
+        $this->dbh = new PDO($dsn, $dbUser, $dbPassword);
+    }
+
+    public function getToken($username, $password, $ip, $sessionId)
+    {
+        $query = 'SELECT id, password FROM users WHERE username = :username:';
+        $sth = $this->dbh->prepare($query);
+        if ($sth->execute(array(':username:' => $username)))
+        {
+            /*
+            audit_log('Unsuccessful login by $username from $ip');
+            audit_log('Could not create token for $username at $ip');
+            return 'Authentication failed. Reason: Internal Server Error';
+            */
+        }
+        else
+        {
+            throw new Exception('AuthFail', self::GWBE_DBERROR);
+        }
+    }
+
+    public function checkToken($token, $sessionId, $ip)
+    {
+        return null;
+    }
+
+    public function removeToken($token)
+    {
+        return null;
+    }
+
+    public function sendSMS($token, $recipient, $message, $passwordLocations)
+    {
+        return null;
+    }
+
+    public function auditLog($ip, $event, $message)
+    {
+        return null;
+    }
+
+    public function messageLog($recipient, $message, $ip)
+    {
+        return null;
+    }
 }
 
diff --git a/smsSender.php b/smsSender.php
index d18d4a8..95cfeae 100644
--- a/smsSender.php
+++ b/smsSender.php
@@ -1,70 +1,62 @@
 <?php
 class smsSender
 {
-	protected $sessionId = null;
+    protected $sessionId = null;
+    protected $backend;
 
-	public function __construct($backend, $sessionId)
-	{
-		$this->sessionId = $sessionId;
-	}
+    public function __construct($backend, $sessionId)
+    {
+        $this->sessionId = $sessionId;
+        $this->backend = $backend;
+    }
 
-	public function login($username, $password)
-	{
-		/*
-		if (valid_user($username, $password))
-		{
-			$token = generate_token($ip, $session_id, $token, $start_time);
-			if ($token)
-			{
-				audit_log('Successful login by $username from $ip');
-				return $token;
-			}
-			else
-			{
-				audit_log('Could not create token for $username at $ip');
-				return 'Authentication failed. Reason: Internal Server Error';
-			}
-		}
-		else
-		{
-			audit_log('Unsuccessful login by $username from $ip');
-			return 'Authentication failed. Reason: Bad username or password';
-		}
-		*/
-		return array('username' => $username, 'password' => $password, 'session-id' => $this->sessionId);
-	}
+    public function login($username, $password)
+    {
+        try
+        {
+            $token = $this->backend->getToken($username, $password, $_SERVER['REMOTE_ADDR'], $this->sessionId);
+        }
+        catch (Exception $e)
+        {
+            throw new Exception('Authentication failed. Reason: ' . $e->getMessage());
+        }
+        $this->backend->auditLog($_SERVER['REMOTE_ADDR'], 'login', 'Successful login by ' . $username);
+        return $token;
+    }
 
-	public function send($token, $recipient, $message, $passwordLocations)
-	{
-		/*
-		if (valid_token($token)
-		{
-			if (send_sms($recipient, $message))
-			{
-				audit_log('Successful message sending by $token->username at $ip');
-				message_log('$message successfully sent to $recipient');
-			}
-			else
-			{
-				audit_log('Message sending failed for $token->username at $ip');
-			}
-		}
-		else
-		{
-			audit_log('Message sending attempt from $ip with invalid token');
-			throw new Exception('Authentication failed. Reason: Invalid Token');
-		}
-		*/
-		return array('token' => $token, 'recipient' => $recipient, 'message' => $message, 'password-locations' => $passwordLocations, 'session-id' => $this->sessionId);
-	}
+    public function send($token, $recipient, $message, $passwordLocations)
+    {
+        /*
+        if (valid_token($token)
+        {
+            if (send_sms($recipient, $message))
+            {
+                audit_log('Successful message sending by $token->username at $ip');
+                message_log('$message successfully sent to $recipient');
+            }
+            else
+            {
+                audit_log('Message sending failed for $token->username at $ip');
+            }
+        }
+        else
+        {
+            audit_log('Message sending attempt from $ip with invalid token');
+            throw new Exception('Authentication failed. Reason: Invalid Token');
+        }
+        */
+        /* TODO: implement */
+        throw new Exception('This feature is not yet implemented');
+    }
 
-	public function logout($token)
-	{
-		/*
-		delete_token($token);
-		audit_log('$token->username logged out at $ip');
-		*/
-		return 'success';
-	}
+    public function logout($token)
+    {
+        /*
+        delete_token($token);
+        audit_log('$token->username logged out at $ip');
+        return 'success';
+        */
+        /* TODO: implement */
+        throw new Exception('This feature is not yet implemented');
+    }
 }
-